cliport/environments/assets/plane/plane.urdf

<?xml version="1.0" encoding="UTF-8"?>
<robot name="plane">
  <link name="planeLink">
  <contact>
      <lateral_friction value="1"/>
  </contact>
    <inertial>
      <origin rpy="0 0 0" xyz="0 0 0"/>
       <mass value=".0"/>
       <inertia ixx="0" ixy="0" ixz="0" iyy="0" iyz="0" izz="0"/>
    </inertial>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 -5"/>
      <geometry>
	 	<box size="200 200 10"/>
      </geometry>
    </collision>
  </link>
</robot>